Ok, I have reviewed a few RD tech products in the past and have been happy and very impressed with all of them.

About a year ago I reviewed the old USB tester and load tester that they offered and they worked quite well at testing USB power ports and to see if USB devices were working or charging like they should.

I have used it far more then I would of guessed since I got it.

They recently released a new version of both the USB tester and Load tester. When they first approached me about reviewing it I was skeptical as I was not sure what you could really improve.

The big selling point seemed to be a Bluetooth app to watch the meter on your phone, which I saw as more of a niche use case.

The I saw the real improvement, the new versions had Micro-USB and USC Type-C input ports!

At first that does not sound like much but this now allows you to test your USB cables to make sure they are not the problem. In addition to being able to use the tester with a cable plugged in instead of being tied to a USB port at odd angles.

I actually had the perfect item I wanted to test this on so I told them to send me a sample for review. Took me longer then I want to admit to get around to it but I finally did.

So I have had 2 of the LII-402 chargers for some time but they would only ever charge 3 cells at a time. I had always thought that the cables could be the problem but when I tried what I thought were better cables it did not fix the problem.

Now I can find out for sure!

At first glance both the USB tester and Load tester are larger then the older versions but also a lot more features. The load tester by itself also now shows voltage for example.

And the USB tester has a much larger and earier to read screen:

So first I set about playing with the features and basic testing, such as the mah counter that shows how much power your device has used:

The voltage graph:

and menu (I recommend upping the screen timeout):

So now to start testing, First I plugged in the charger with some drained cells to the tester and decided to see what happens.

It would gladly pull 1A but anytime I tried to start more then 2 cells charging it would stop them and just would not go above 1A.

So now to test the Cable, I unplugged the charger and plugged the cable into the load tester to get an idea of what was going on, at 1A it was only getting 4.6V to the load tester:

At 2A it was at 4V (now it was lower then normal since there were 2 cables but the outcome is the same)

Thus this seemed to confirm my idea that the cable was the issue. So I tried my known good cable with the charger and sure enough, it worked perfectly!

Then I got down to the technical testing. I connected the tester directly to the USB power adapter and took a baseline voltage reading by holding the next button on the following screen with 1A of current being pulled through it. This records the input voltage from the power adapter at this current.

After that I disconnected the tester and then plugged in the cable in question to the same power adapter (so the input voltage would be the same) and to the tester input and turned the 1A load back on. I then held the next button again so it can run the calculation and here is the result:

No wounder it was shutting down with more then 3 cells charging, it was only seeing at most 4.1V! The stock cable with the LII-402 has a whopping 762mohm’s of resistance.

To put them in perspective my good cables had around ~150-200ohms with most in the 300-500ohm range.

I then set about testing all the other cables I had, finding that you really can not judge a book by it’s cover. Some I was sure would suck were not bad and some I thought were good were bad.

I ended up just connecting the cables to a 1A load and seeing what the voltage was, anything over 4.5v passed as usable. Anything over 4.75v was good. I had 2 that were over 4.9v that are very good.

Overall well worth the time and money IMHO to finally be able to scientifically sort all my cables and figure out which ones to keep and which to toss aside.

I did not try the Android app myself as I don’t install random apps unless I can’t help it but I looked it up and it looks nice. Good for watching things from afar.

lol, once you get in the groove it moves fairly quickly. I actually found a box with about twice as many cables as the picture and sorted through them all.

I think I ended up with about 30% that were basically unusable (backed up by many of those giving me issues in the past), 30% were passable for basic small things and the rest were split between good cables and better cables.

The highest AWG cable I could find that is in the micro-USB category was by Anker with 20AWG power wires.

Still, 18AWG on a USB cable is mind boggling to say the least. Would be extremely good to test USB powerbanks and see if the manufacturer is padding the numbers, and not having to worry about a cable losing a ton of energy to heat.

Thanks for posting this! I just got a new phone and been researching USB type C. Studying up on chargers and cables is a must. If you go cheap or buy the wrong cable or charger you could easily brick you phone.

I’ve been testing a lot of my USB cables last night… most of them came from the factory with various USB devices that I bought.
Just about all of them seem to have fairly high resistance, aside from a Blitzwolf USB C cable I paid good money for and a 6-inch Cable Creations one – that one has low IR primarily because it’s so short.

I try to order shorter USB cables these days, to help keep IR low. I just ordered a micro USB 1.5 ft UGreen one plus another 1.5 ft one from Monoprice – I’ve seen some positive comments about them. Let’s see.

The method I showed you earlier does not take into account the power supply voltage dropping under load.

The power supply I’m using has a voltage display, and I can see it dropping slightly under load. For example, at idle it’s at 5.26V. At 1A it’s at 5.24V. So, could I use this information in conjuction with voltage data from the DROK load tester to more accurately calculate cable resistance?

Quote:

You need a USB meter like the UM25C to calculate a single cable’s resistance.

Yes, but you need a power supply that supports QC 3.0 or one without voltage cable compensation.

I’ve tested it today on my dual USB power supply featuring QC 3.0 and USB-A 2.4A, and the USB 2.4A was compensating for the voltage drop, to the point the voltage under load was higher in some instances than the idle voltage.

Testing using the QC 3.0 port netted much more accurate and reliable results.

TLDR: Find a USB port that doesn’t do voltage compensation. Techs like SmartID/VoltageBoost do this.

Edit: Looks like your USB supply does do voltage compensation. Find one that has QC 3.0, which doesn’t do cable compensation unless the protocol is activated.

I have a USB C power supply that came with my Pixel2 phone that can output 9V, but I don’t believe it is technically QC3.0. I think Google uses some other coding scheme. The HD35 probably will not be able to trigger it.

We find that the cable’s resistance is 0,03Ohm, or 30mOhms as stated before. This is for the 0,50m cable BTW. The 1,00m cable would be 0,060Ohm, which still are the lowest resistance cables that I’ve EVER FOUND.